1. Field of the Invention
The present invention relates to an apparatus and method for diagnosis memory (RAM and ROM) used in microcomputers for controlling electronic control devices for automobile engines and the like.
2. Description of the Related Art
Heretofore, in automobile engine control devices, in addition to self diagnose of the CPU of the control microcomputer, the CPU also diagnoses the memory such as RAM and ROM. To be specific, when power is applied, before the engine starts, the whole memory region is subjected to a read-write check for the RAM, and a sum check or parity check for the ROM.
Furthermore, with control devices such as electronic controlled throttle valves that directly affect engine behavior, it is necessary to detect memory malfunctions that occur while the engine is operating.
However, because memory diagnosis takes time, memory diagnosis while the engine is operating could affect the engine control functions during the diagnosis.
The present invention takes into consideration the above heretofore problem, with the object of providing real time diagnosis of the whole memory region without affecting the control functions.
Accordingly, with the present invention, there is provided a high speed diagnosis device for performing continuous diagnosis over a whole memory region prior to using the memory or after using the memory, and a low speed diagnosis device which interrupts the memory being in use at predetermined periods to intermittently perform diagnosis on divided part of the memory each time, to construct an apparatus for diagnosing a microcomputer memory.
Thus, before or after the memory is in use (while memory is not in use), memory diagnosis is performed by the high speed diagnosis which performs continuous diagnosis of the whole memory region. On the other hand, when the memory is in use, diagnosis is performed by the low speed diagnosis which interrupts the memory at predetermined periods to intermittently perform diagnosis on divided part of the memory each time. Hence real time diagnosis of the whole memory region is effectively enabled without affecting the control functions.
The high speed diagnosis device may perform diagnosis with time synchronous jobs, with each job diagnosing a number of bytes obtained from previously determined diagnosis unit bytes multiplied by a set number of cycles.
Thus, high speed diagnosis that performs continuous memory diagnosis of the whole region is possible.
The low speed diagnosis device may perform diagnosis with time synchronous jobs once in a plurality of cycles, with each job diagnosing previously determined diagnosis unit bytes.
Thus, low speed diagnosis suitable for RAM whose capacity is comparatively small is possible.
Alternatively, the low speed diagnosis device may perform diagnosis with time synchronous jobs, with each job diagnosing previously determined diagnosis unit bytes.
Thus, low speed diagnosis suitable for ROM whose capacity is comparatively large is possible.
When diagnosing a memory used in an engine control microcomputer, the high speed diagnosis device diagnoses the memory before the engine is started or when the engine is stopped, and the low speed diagnosis device diagnoses the memory while the engine is operating.
Thus, real time diagnosis of the whole memory region is possible without affecting the control functions of the engine while the engine is operating.
Characteristic features of the present invention and the resultant operation and effects will become more apparent from the embodiments described hereunder.